The invention relates to a bypass cooling assembly adapted to carry the heat away from bearing assemblies such as radial, thrust and sleeve bearings of the non-flooded housing type.
A segmented bearing assembly is known and includes a plurality of arcuate pads, each tilting through a small angle so as to create a thin wedge shape opening between a shaft and an inner surface of the pad. The opening allows developing a film of oil which supports the load. However, because the film of oil interface is sheared as the oil is dragged through the bearing interface, the oil temperature rises. If the oil temperature rises sufficiently, its viscosity falls, and if the temperature rises substantially, its viscosity falls to a point where there is a direct rubbing of the metal shaft on the metal bearing surfaces, resulting in greater friction which may increase the bearing temperature to destructive level. Also, Babbitt softens at high temperatures and moves or xe2x80x9cwipesxe2x80x9d due to the shearing forces causing direct metal to metal rubbing.
It is also known that some power loss in tilting pad bearing assembly results from churning the oil after it passes out from underneath the trailing end of the pads. Churning imparts energy to the oil and elevates its temperature. Furthermore, since it is necessary to have some space between the leading and trailing edges of the spaced apart pads to allow the pads to tilt, hot oil emerging from the pad and shaft interface at the trailing end of one pad is carried by the shaft under the leading end of the next ensuing pad contributing to elevated temperatures. Also, cool inlet oil mixes with the hot oil from the pad trailing edge in the space between pads, elevating the temperature of the inlet oil before it enters the next pad""s leading edge.
U.S. Pat. No. 5,738,447 to Nicholas, which belongs to the same assignee as the present application and is fully incorporated herein by reference, discloses a non-flooded housing wherein the end seals are wide open and additional drain holes are located in the housing to allow the lubricating oil to exit the housing immediately. The assembly includes a spray bar blocker effectively blocking the hot oil that exits the trailing edge of one pad from mixing with the cool inlet oil. In addition, cool lubricating oil is injected directly onto the leading edge of the next pad.
A material made of C18200 Chrome Copper or Ampcoloy(trademark) copper-based alloy known for its excellent thermal conductivity has been successfully utilized for many years in tilting pad journal and thrust bearings having a flooded bearing shell. This design allows lubricating oil to carry the heat away from the Ampcoloy(trademark) surface at the back and edges of the tilting pads. It is this oil that eventually drains out of the bearing housing carrying away the heat conducted by the Ampcoloy(trademark) away from the babbitt surface.
However, sleeve and segmented bearings having a non-flooded housing design cannot effectively use pads or sleeves made of Ampcoloy(trademark), since the non-flooded structure has no means for carrying the heat away from the tilting pads or from the shell.
It is, therefore, desirable to provide a cooling bypass assembly used in conjunction with a segmented bearing, such as tilting pad journal and thrust bearings having a non-flooded housing, and with a sleeve bearing made predominantly of copper in a such a manner that cool inlet oil carries heat away from the pads and sleeve without interfering with a lubricating process.
A bypass cooling system including a plurality of heat-transfer chambers, which are strategically located in a bearing assembly having a non-flooded housing and a plurality of blocker bars, effectively carries away the heat from the pads and the sleeve.
In accordance with one aspect of the invention, a sleeve bearing assembly preferably manufactured from C18200 Chrome Copper or Ampcoloy(trademark) has a non-flooded bearing shell which is cooled by inlet cool oil. The cool oil is introduced into circumferential heat transfer chambers or grooves in the vicinity of the bearing""s top-dead-center location. Gravity and the inlet oil pressure drives the oil into these heat transfer chambers and further down to the bottom of the bearing shell. Along the way, the cool inlet oil picks up the heat conducted away from the babbitt surface by the Ampcoloy(trademark). Eventually, the cool oil runs directly to the oil drain and is never involved in the lubricating process.
In accordance with another aspect of the invention, a bypass cooling assembly has a plurality of circumferential heat transfer chambers formed along the outer surface of tilting pads of a tilting pad journal bearing, wherein the tilting pads are housed in a non-flooded housing. Cool inlet oil runs along the chambers, which are machined on the outer face of the pads, and picks up the heat conducted away from the babbitted inner and side surfaces of the pads.
According to still another aspect of the invention, a bypass cooling assembly for carrying the heat away from copper pads includes a combination of radial and axial supply channels delivering inlet cool oil into a plurality of circumferential channels, which are machined within the pads. Similarly to the above-discussed modifications of the bypass assembly, this structure allows the heat to be carried away from the babbitted surfaces of the Ampcoloy pads.
The term xe2x80x9coilxe2x80x9d is used herein as generic to any liquid lubricant that can be used to cool and lubricate the bearings encompassed by the present inventions.
It is an object of the invention to provide a bypass cooling assembly in bearing assemblies predominantly made from copper and characterized by non-flooded housings.
Still another object of the invention is to provide a bypass cooling assembly for a sleeve bearing assembly wherein cool inlet oil does not interfere with a lubricating process.
Another object of the invention is to provide a bypass cooling assembly for a tilting pad journal bearing assembly having a non-flooded housing.
A further object of the invention is to provide a bypass cooling assembly wherein the outer surface of tilting pads is formed with heat transfer chambers preventing cool inlet oil from mixing up with lubricating oil.
Yet a further object of the invention is to provide a bypass cooling assembly wherein a series of heat transfer chambers are machined within the tilting pads between the opposite outer and inner surfaces.
Still another object of the invention is to provide a bypass cooling assembly in a segmented thrust bearing.